Rename course activity settings and add lang string

Details

Description

In Moodle 2.5 course activity settings sections are closed by default. In quiz module there are two sections names 'Layout' and 'Display'. Its nor intuitively understandable what the settings in the sections are and what the difference is. May be native speaker have a clear understanding but others don't.

While trying to find a better trm we found that the string 'Display' is not a quiz modul internal string but a core string. It makes sense to create an individual string for the section to make clear what it is. Otherwise we will have changes in other contexts wherethe strig is used alos..